The present invention relates to wellbore fluids (especially, synthetic fluid-based drilling fluids) and systems and processes for using then in a subterranean formation in oil and gas recovery operations.
While drilling fluids employing synthetic fluids (such as polyalphaolefin- and ester-based drilling fluids) as the base fluid are capable of achieving 96 hour LC.sub.50 Mysid shrimp (Mysidopois bahia) bioassay test results greater than 100,000 ppm, their commercial use has been severely restricted because of the high cost of the synthetic fluids.